Method of center spotting container closures and apparatus therefor



Oct. 24, 1939. A. H. WARTH' ET AL METHOD OF CENTER SPOTTING CONTAINER CLOSURES AND APPARATUS THEREFOR Filed Nov. 11, 1936 J ibth/ 7 70611170 Patented Oct. 24, 1939 PATENT OFFICE METHOD OF CENTER SPOTTING CONTAIN- ER. CLOSURES AND APPARATUS THERE- FOR Albin n. Warth and Emil Gassmann, Baltimore, Md., asaignors to CrownCork & Seal Company, Inc., Baltimore, Md.. a corporation of New York Application November 11, 1936, Serial No. 110,342

method and apparatus for applying "center spots" to cushion discs used in container closures. By "center spots is meant facings of less diameter than the cushion discs and adhesively secured centrally to the cushion discs as disclosed in the patent to McManus, No. 1,339,- 066, granted May 4, 1920.

The facing is punched from strip material which may be metal foil or paper having an exposed facing of varnish or other suitable material, such as chlorinated rubber. The center spots are united to the cushion discs by a thermoplastic adhesive, such as gutta percha or nitrocellulose-resin material disclosed in the patent to Warth, No. 1,956,481, granted April 24, 1934. The method heretofore employed for applying center spots is broadly disclosed in the patent to Warth, No. 1,967,195, granted July 17, 1934. In the practice of this method may be used apparatus such as is disclosed in the patent to Johnson, No. 1,852,578, granted April 5, 1932.

The present invention relates to certain improvements upon the method and apparatus of the aforesaid Warth and Johnson patents.

An object of the invention is to provide a method and apparatus which will produce a firmer, more uniform, and more permanent adherence of the center spot to-the cushion disc. More particularly, the invention aims to pro- ,vide an improved method for treating the spot after it has been initially united to the cushion d sc by the punching operation. The initial union of the spot and cushion disc is obtained usually by preheating the cork disc and then punching from a i thermoplastically coated strip a center spot which/is. deposited upon the preheated disc in the punching operation. In some instances, the punch itself may be heated somewhat, either in addition'to or in lieu of preheating the cork disc:

Heretofore, in the application of spots by thermoplastic adhesives of the character above mentioned, it has been customary to maintain the center spots under pressure while they are permitted to cool at least to room temperature, as by a dial having a multiplicity of piessure plungers which maintain the spots under pressure while the adhesive is cooling and becoming set. In some instances, such dials have been positively cooled to insure a quick, positive setting of the thermoplastic adhesive while the crown is maintained under pressure. We have found that improved results are obtainable with thermoplastic adhesives if the center sp t Wh le being subjected to pressure for a considerable period (approximately 4 to 10 seconds), for example in the dial which holdsthe crown under continuous pressure for from 1 to 10 seconds, is subjected to heat substantially higher than room temperature. A sharp or sudden cooling of the adhesive is thus avoided. We prefer that the effective heat be somewhat lower than the heat previously used to obtain t'acking" or fusion of the adhesive and union of the spot and cushion disc, so that there is a slight cooling while the crown is under pressure. Thereafter, the crowns are discharged and permitted to cool in the atmosphere. We have found that with nitro-cellulose-resin adhesives particularly, and in some cases with gutta-percha, the relatively rapid cooling under pressure which is produced, for example, by cooling in a pressure dial which is at room temperature or positively cooled, does not produce a centerspot which is bonded to the cushion disc as effectively as one. produced in accordance with the method herein described. Although it has been thought, heretofore, that a relatively rapid cooling under continuous pressure, as in the dial, is desirable with thermoplastic adhesives, the rate of cooling being sometimes increased by positive cooling of the dial, we have discovered that this procedure is not as satisfactory as the present method in which a temperature higher than room or atmospheric temperature is maintained in the crown while it is subjected to this continuous pressure. 7

The temperature to which the spot is subjected while under continuous pressure, as in the dial,

varies with the different thermoplastic. adhesives employed. The temperature to be controlled is the effective temperature, 1. e., the actual temperature to which the adhesive is raised, since, aswill be understood, the adhesive does not necessarilyrise to the temperature of the heat applying instrumentality. The actual temperature to which the adhesive is raised, is determined not only by the temperature of instrumcntality, but by the time to which the spot is subjected to such an instrumentallty. We find that it is preferable to maintain the spot and the adhesive at a temperature which will permit the adhesive to effect a firm bond of the spot to the cork and retain such bond when the crown is relieved from pressure and permitted to cool under atmospheric conditions. The pressure is ordinarily relieved by discharging the crowns from the dial, and they are permitted to cool in the conveyors and bins into which they are dis- 7 charged.

In our preferred method, we use an eifective temperature appreciably below the temperature towhich the spot has been subjected in obtaining the tacking of the adhesive and the union of the spotv to the cushion disc, withthe result that, although the adhesive is maintained in a somewhat plastic condition while under continu*. ous pressure. is not as tacky or plastic as in previous stages of the method. For example. when using a nitro-cellulose-resin adhesive, we maintain the crowns in the dial at a temperature of approximately 1251". when the crowns enter the dial, the surfaces of the cushion discs in contact with the adhesive are at a temperature of approximately 130 E, and the adhesive is quite tacky. when the crowns leave the dial, the surface of the cork disc is at a temperature of approximately 110 F.. and the adhesive is not appreciably tacky. Although the temperature in the dial is approximately 1125' F. or only slightly less than the tacking point of such an adhesive, the gradual transition of the adhesive from a tacky to a non-tacky condition is due to the decrease in eifective heat from the preceding stages of the method.

' when using gutta percha wlth paper spots suitably coated. for example with chlorinated rubber. the temperature of the surface of thecork'disc as it enters the dial and of the adhesive is from 100 1". to 115' ll. and the adhesive is quite tacky. The effective temperature of the adhesive in the dial is from 80 1". to 90 It. and the temperature of the cork disc surface when it leaves the dial is about the same. The temperature of the dial plungers to which the crown is subjected. is approximately 90 1. to 105 E, and although this is only slightly lower than the tacking point of gutta-percha (approximately 130 E), the eifective heat applied to the gutta-percha is lower than the temperature to which the gutta-percha has been subjected before the crown enters the dial. when the crown leaves the dial the gutta-percha. although slightly tacky. is considerably less tacky than when it enters the dial and the crowns are immediately discharged and permitted to cool without pressure and in the atmosphere.

By this method. there is obtained a firmer. more permanent, and more uniform adhesion of the spot to the cushion disc throughout the entire area of the spot than in methods heretofore employed with thermoplastic'adhesives and in which the spot is subjected to atmospheric or subatmospheric temperature while maintained under continuous pressure in the cooling dial.

Another feature of our improved method has to do with the treatment of the center spot crown between the time the spot is deposited on the preheated cushion disc by the punch and the time it is. subjected to the substantially continuous pressure in the dial. Heretofore. it has been the practice, immediately following the punching operation and deposit of the spot, at which time the spot is subjected simultaneously or instantly with deposit to heat and-pressure. to subject the deposited and preliminarily adhered spot to one or more heated plungers, as described for example in the patents above mentioned.

In practice, these plungers are raised to a heat of approximately 500 to 550 1"., and their purpose has been to subject the crown to combined plungers. We have found that this so-called "flash and impac "treatment of the spot is, in some cases, undesirable. and that improved results may be obtained by subjecting the spot to a relatively lower temperature, over a substantially longer period of time, preferably in the absence of impact or pressure and before the crown is subjected to continuous pressure in the dial. That is to say, instead of subjecting the spot immediately after deposit to impact by use heat applied by radiation, as from a heated go metallic tunnel or bar. The bar may be raised to the desired temperature by an internal electrical resistance. The tunnel wall maybe heated by directing against the exterior thereof a gas fiame from which the spotis protected by the g5 tunnel. The heating should extend along and over the path of the spots for a considerable distance as irom 8" to 24" and substantially to the dial entrance. The heater is spaced approximately above the spots. This temperature will be increased as the length of the heating 1 instrumentality is shortened, and in no case should the effective heat applied be above that which will injure or affect the physical condition of the facing material or be below that which is necessary in relation to the length of the bar or distance of travel of the crowns in the heated area necessary to insure a thorough tacking of the adhesive. The heat of the bar must, of

course. be regulated in accordance with the heat 0 necessary to obtain this tacky condition before the spot enters the dial and in relation to the speed of travel of the crowns in their path beneath the heated her, since the speed of travel determines the time or period to which the spots 5 are subjected to heat and as a consequence the eifective heat imparted to the adhesive. In some cases, we may use instead of a bar or so-called "strip" heater, a multiplicity of plungers each having a relatively low heat not higher than that which will injure the facing material, and not lower than that which in relation to the numberof plungers and consequent time to which the spots are subjected to best. are necessary to render the adhesive sufliciently tacky. These plungers should exert very little pressure upon the spot to avoid exuding or disturbing the adhesive.

As stated above. we prefer a strip heater in order to avoid the impact which has a tendency so to disturb the distribution of the relatively tacky adhesive and to force the adhesive beyond the edges of the spot. But whether a strip heater or plunger heaters are used, the temperature must be carefully controlled. as by suitable thers5 mostatic means. to insure that the eifective heat. 1. e., the temperature to which the spot is raised, is not above that which will injure or aifect the physical condition of prop rties of the spot material or below that required to obtain the desired tackiness of the adhesive. y

Heretofore, it has been thought that relatively high temperatures and also pressure instantly following the punching operation are essential.

We have found that improved results are obby utilizi ginstead a relatively slow heating or- "soaking" of the spot with a relatively low heat, preferably in the absence of impact, as by a strip heater, an improved product is obtained.

In the accompanying drawing. we have shown somewhat diagrammatically a suitable apparatus for carrying out our improved method, and in the drawing:

Figure 1 is a top plan view.

Figure 2 is a fragmentary side elevational view.

Figure 3 is a cross-sectional view substantially on the line 3-3 of Figure 2.

Figure 4 is a fragmentary sectional view showing the relationship of the heating means to the plungers in the dial, and

Figure 5 is a detail view showing a modified form of heating means.

Referring to the drawing more in detail, the crown caps having the cushion discs therein are shown as supported in a guideway I0 (Figure 3) on the bed Ii and along which they are fed by suitable means (not shown). The cushion .discs are first passed beneath a preheater I! which may be an elongated gas flame or any other suitable instrumentality, such as shown for example in the patent to Johnson above men'- tioned. The feeding means, which is of the usual character described in the aforesaid patent, and has a stop and go motion, next positions the crowns successively beneath a punch [3 which punches the spots from a web ll of spotting material such as foil or paper suitably coated with varnish or other coating means, such as chlorinated rubber, The web is fed beneath the punch by suitable means (not shown) and a coating of thermoplastic material on its undersurface is softened as soon as the spot punched from the web strikes the preheated cork disc. Instead of preheating the cork disc'or in addition thereto. the punch may be suitably heated, if desired. The object is simply to insure that the application of heat and pressure to the spot atthe instant it strikes the cork disc to obtain an immediate adherence of the spot to the disc in the central position it is deposited. The adhesive on the lining material may be gutta percha, nitrocellulose-resin thermoplastic or any other suitable thermoplastic material.

The spotted crowns with the spots initially adhered are then progressed through a heated zone which may be created by'means of a metallic tunnel I5 (Figure 3) supported by brackets it from the bed. This tunnel may be heated in any suitable manner, as by an elongated gas flame H which plays directly upon the exterior surface of the tunnel, thereby maintaining the interior of the tunnel at the desired temperature. The heated zone may be from 6 to 24" in lengthy and extends substantially to the rotating dial l8 which corresponds in general construction to the dial shown in the Johnson patent above mentioned. This dial has a series of plungers l9 which are lifted at the entrance to the dial, but descend and apply pressure to the spot which is held under continued pressure until the dial carries the crown substantially 360 to the point of discharge. The plungers in the dial are maintained suitably heated as by a gas flame 20, which plays directly upon the plungers as they pass through a portion of their cycle and it is found that a flame approximately 6" in length will maintain the plungers at the desired temperagainst the bed.

aturc. At times, it may be found desirable, particularly in the cold weather, to provide a source of additional heat, and for this purpose weprovide an auxiliary gas burner 2| beneath the bed of the dial, having flames which play upwardly Ordinarily, this additional burner will be found unnecessary but it may be used to supplement the heater 20 which is directed against the plunger.

Referring to Figure 5, there is shown a modified form of heater element which may be used in lieu of the heater I! and tunnel l5. This heater consists of a hollow bar or rod which may be from 6 to 24" in length and has an internal electrical resistance element which raises the bar to the desired temperature. A heater of this character may be accurately regulated by suitable thermostatic controls.

Although we have not shown in the drawing the details of various features of the machine, such as the chute from the crown hopper and the feeding mechanism for the. thermoplastically coated web, it will be understood that these features are old in the art, as shown for example by the patent to Johnson, above mentioned, which discloses all features of the mechanism not specifically described herein. It will be understood that'the invention is not limited to the details illustrated and described, and that such modifithereafter subjecting the spot to further heat without pressure, and thereafter maintaining the spot under pressure continuously for several seconds while subjecting the spot to heat.

2. The method of center spotting cushion discs of container closures with facings of less diame-- ter than the discs which consists in punching a center spot from a strip of spot material having on one surface a coating of thermoplastic adhesive, depositing the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation applying pressure and sufllcient heat to render the adhesive tacky and secure an initial stick, immediately thereafter subjecting the spot to further heat, and thereafter maintaining the spot under pressure continuously for several seconds while subjecting the spot to heat somewhat less than that utLlized previously to obtain the adhesion.

3. The method of center spotting cushion discs of container closures with facings of less diameter than the discs which consists in punching a center spot from a strip of spot material having on one surface a coating of thermoplastic adhesive, depositing the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation applying pressure and suflicient heat to render the adhesive tacky and secure an-initial stick, immediately-thtreafter subjecting the spot to further heat without pre sure, thereafter maintaining the spot under pressure continuously for a period of approximately several seconds while subjecting the spot to heat, and then permitting the spotted disc to cool under atmospheric pressure and temperature.

4- The method of center spotting cushion discs of container closures with facings of less diameter than the discs which consists in punching a center spot from a strip of spot material having on one surface a coating of thermoplastic adhesive, depositing the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation applying pressure and 'suflicient heat to render the adhesive tacky and secure an initial stick, immediately thereafter subjecting the spot to further heat, thereafter maintaining the spot under pressure continuously for a period of several seconds while subjecting the spot to heat somewhat less than that previously utilized to obtain the adhesion, and then permitting the spotted disc to cool under pressure and atmospheric temperature.

5. The method of center spotting cushion discs or container closures with facings of less diameter than .the discs which consists in punching .a center spot from a strip of spot material having on one surface a coating of thermoplastic adhesive, depositing the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching-operation applying pressure and sufllcient heat to render the adhesive tacky and secure an initial stick, immediately thereafter moving the spotted disc through a heated zone in which the spot is maintained free of pressure and thereafter cooling the disc under continuous pressure.

6. The method of center spotting cushion discs of container closures with facings of less diameter than the discs which consists in punching a center spot from a strip of spot material having on one surface a coating oi-thermoplastic adhesive,.deposlting the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation applying pressure and suilicient heat to render the adhesive tacky and secure an initial stick, immediately thereafter moving the spotted disc through a heated zone in which the spot is maintained free of pressure and thereafter cooling the disc under continuous pressure while subjecting the same to heat of'a degree less than that previously utilized to obtain the adhesion but substantially above atmospheric temperature whereby to prevent a sharp or sudden cooling.

7. The method of center spotting the cushion discs of container closures with facings of less diameter than the discs and adhered to the discs by nitrocellulose-resin thermoplastic adhesive. which consists in punching a center spot from a strip of spot material having on one surface a coating or the thermoplastic adhesive, depositing the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation applying pressure and suiilcient heat to the spot to render the adhesive tacky and secure an initial stick, immediately thereafter subjecting the spot to further heat and then maintaining the spot under continuous pressure while moving the spotted disc and while subjecting the spot to a degree of heat suflicient to prevent a sharp or sudden cooling but sufliciently low to permit the adhesive to become relatively non-tacky.

8. The method of center spotting the cushion discs of container closures with facings of less.

diameter than the discs and adhered to the discs "by nitrocellulose-resin thermoplastic adhesive.

which consists in punching a center spot from a strip of spot material having on one surface a coating of the thermoplastic'adhesive, depositing the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation applying pressure and suilicient heat to the spot to render the adhesive tacky and secure an initial stick, then passing the spotted disc through a heated zone in which the spot is subjected continuously to heat while moving, and then maintaining the spot under continuous pressure while moving the spotted disc and subjecting the spot to a degree of heat sufllcient to prevent a sharp or sudden cooling but sufliciently low to permit the adhesive to become relatively non-tacky.

9. The method of center spotting the cushion discs of container closures with facings of less diameter than the discs and adhered to the discs by nitrocellulose-resin thermoplastic adhesive,

which consists in punching a center spot from a strip of spot material having on one surface a coating of the thermoplastic adhesive, deposits ing the spot on a cushion disc in the punching opcrai'ion, simultaneously with the deposit and in the punshing operation applying pressure and sufllcient heat to the spot to render the adhesive tacky andsecure an initial stick, then passing the spotted disc through a heated zone in which the spot is subjected continuously to heat while moving but is'maintained free of pressure, and then maintaining the spot under continuous pressure while moving the spotted disc and subjecting the spot we degree of heat sufficient to prevent a sharp or sudden cooling but suiiiciently low to permit the adhesive to become relatively non-tacky.

10. Apparatus for center spotting cushion discs of container closures comprising means for feeding cushion discs along a predetermined path and successively operating devices for adhering center spots thereto comprising means for punching from a thermoplastically coated web and applying center spots to the successive discs in the,

punching operation under heat and pressure, means immediately following said punching means positioned above the path of travel of the spotted discs for heating the same by radiation and without pressure thereon as they are moved along said path, and a rotating dial having pressure plungers for receiving the cushion discs and for maintaining the same under pressure during the rotation of the dial, said dial having associated therewith means for maintaining the spotted discs while under pressure therein at superatmospheric temperature 1 11 The method of center spotting cushion discs of container closures with facings of less diameter than the discs which consists inpunching a center spot from a strip of spot material having on one surface a coating of thermoplastic adhesive, depositing the spot on .a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation applying pressure and sumcient heat to render the adhesive tacky and secure an initial stick, then moving the spotted disc through a heated zone in which the spot is maintained free of pressure having on one surface a coating of thermoplastic adhesive, depositing the spot on a cushion disc in the punching operation, simultaneously with the deposit and in the punching operation apply- 5 ing pressure and sumcient heat to render the adhesive tacky and secure an initial stick, then moving the spotted disc through a heated zone in which the spot is maintained free of pressure and then subjecting the disc to pressure continuin: tor several seconds.

- ALBIN H. WARTH.

EMIL GASSMANN. 

